I'm having the same issue when using a shield TV pro 2019 sound is clicking/cherping when watching Amazon prime YouTube or Netflix did you resolve the issue? The sound on my 55oled903 was also good when we first had the TV but has worsened over the last two weeks.
Registered myself specifically for this issue. I have the same issue, 55OLED903 have it for +/- 7 months now and recently the sound is having issues as described by original poster. Netflix, amazon prime etc. BUT here in The Netherlands I can watch Netflix also using their top media box , when watching Netflix on the media box there are no sound issues at all. Watching regular tv also no issues. So I think it has to do with the android software somehow and it’s not hardware related.
If someone has an update , let us know !
A firmware update was released on the 12th of December to fix a number of audio related issues, including a faster EPG. (no sound now when you search the TV guide ) however after the update you then have to complete a factory reset that resolved any audio related issues. Initially I thought it was my Nvidia shield 2019 pro, but upto now it seems as though it's the TV. Hopefully the above information will assist you to rectify your issue..